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Pdf was developed as a format for printing. And the same features which make it good for printing also make it usable for scanning archived books. But it is widely used for other articles and other ebooks. And it isn't suitable and creates a number of accessibility challenges.
A few weeks ago, I picked up a pdf-only book about accessibility. It wasn't very accessible, and it didn't address some of my accessibility needs.
Because it's designed to display page by page, it can't easily reflow. Instead users are supposed to move about within each page. On older e-readers, that's incredibly slow. On newer ones, zooming, panning, etc. can trigger migraines. Because most publishers are fond of large pages with 2 columns, that requires a lot of extra movement.
Because it's designed as a final format before printing, it can't always be converted to epub or mobi or other reflowable formats. Text gets lost, or scrambled. Because many publishers are fond of extra images framing each page, it can create a lot of extra clutter.
Because newer pdfs are often incompatible with older devices, it often requires pdf-to-pdf conversion. Willus's k2pdfopt or k2opt is the most powerful tool for that, but it rasterizes everything, so it's better for scanned pdfs. Ghostscript with pdfwriter and a suitable compatibility level's not as powerful, but it doesn't rasterize everything, so it's usually better for pdf-born-pdfs. It sometimes loses text though, and sometimes fails to process images if they're set up as mosaics of small blocks.
Corrupt or garbled text in the original, or after pre-processing with Ghostscript, make pdfs unsearchable, and much harder to navigate. I expect they also make these pdfs incompatible with screen readers. Even the out-of-order text which is so common could make them incompatible with screen readers.
On a map or counter-sheet where exact appearance and size are important, it's probably still the best choice. But for articles, rules, ebooks, etc. please consider alternatives.
A few weeks ago, I picked up a pdf-only book about accessibility. It wasn't very accessible, and it didn't address some of my accessibility needs.
Because it's designed to display page by page, it can't easily reflow. Instead users are supposed to move about within each page. On older e-readers, that's incredibly slow. On newer ones, zooming, panning, etc. can trigger migraines. Because most publishers are fond of large pages with 2 columns, that requires a lot of extra movement.
Because it's designed as a final format before printing, it can't always be converted to epub or mobi or other reflowable formats. Text gets lost, or scrambled. Because many publishers are fond of extra images framing each page, it can create a lot of extra clutter.
Because newer pdfs are often incompatible with older devices, it often requires pdf-to-pdf conversion. Willus's k2pdfopt or k2opt is the most powerful tool for that, but it rasterizes everything, so it's better for scanned pdfs. Ghostscript with pdfwriter and a suitable compatibility level's not as powerful, but it doesn't rasterize everything, so it's usually better for pdf-born-pdfs. It sometimes loses text though, and sometimes fails to process images if they're set up as mosaics of small blocks.
Corrupt or garbled text in the original, or after pre-processing with Ghostscript, make pdfs unsearchable, and much harder to navigate. I expect they also make these pdfs incompatible with screen readers. Even the out-of-order text which is so common could make them incompatible with screen readers.
On a map or counter-sheet where exact appearance and size are important, it's probably still the best choice. But for articles, rules, ebooks, etc. please consider alternatives.
